Blog
Electrical Protection of Induction Motors
Wednesday, January 30, 2019
Three-phase induction motors have a wide variety of applications in commercial and industrial settings. These include heat pumps, air conditioners, compressors and industrial machinery. Given their extensive range of applications, it’s critical to adequately protect 3-phase induction motors. Operating these kinds of motors requires protection against several different events and conditions. In this post, we’ll help you understand those.
Fault Protection
Electrical fault can occur if electric current is abnormally high. Generally, fault currents result from short circuits, line-to-line fault, and line-to-ground fault. In case of motor, fault current can occur if the motor fails to start because of a locked rotor. The duration of fault current will be very short if the motor is able to start normally. However, it’ll extend if motor doesn’t start.
Circuit breakers with “magnetic tripping system” are used to accomplish fault protection. Solenoid coil in these circuit breakers induces a powerful magnetic which causes the motor’s contacts to open. Thus the electric supply to the motor is interrupted. If fault is not interrupted, it can cause permanent damage to the motor.
Overload Protection
When the motor’s current is above its rated value, it is called overload. However, unlike fault current overloads, this current may be a few amperes greater than the motor’s rated current. Nevertheless, motors must be protected against overload as it can cause permanent damage. Electronic protection or thermal protection devices can be used to accomplish overload protection.
- Typically, thermal protection is based on the motor’s contacts. When the current exceeds the motor’s rated current, a thermal protection device interrupts the circuit.
- The same result is achieved electronic protection, but through the use and measurement of contactor.
There’s a time delay in overload protection. The reason is that short-durations of over-current conditions are normal in some operations and the protector should allow it.
Over-Voltage/Under-Voltage Protection
Electric motors must be operated within a certain voltage range. If the operating voltage is outside that specific range, problems can occur shortening the motor’s service life. In case of under-voltage, the motor draws more current to maintain the required torque. This damages motor and causes a higher inrush current. In case of over-voltage, the ferromagnetic cores of the motor become saturated, increasing the line current.
Normally, motors have a built-in protection circuit which disconnects the equipment if the voltage exceeds or falls below the specified voltage range.
Phase Imbalance/Phase Loss Protection
If one of the three phases of an induction motor is lost, it can still continue operating. However, when the motor operates without all three phases, it not only puts more mechanical stress on equipment but also increases the current in the other two phases. The condition may cause the motor to fail.
An auxiliary circuit is used to protect the motor from phase imbalance and loss. Phase imbalance should typically not be greater than 2 percent to ensure optimal performance.
For more information, feel free to contact us at Midwest Equipment! We'll be happy to answer all your questions.
|
|
Recent Posts
How to use Gateway Convertors
Wednesday, March 10, 2021
Voltage Monitor Relays
Wednesday, December 9, 2020
Why do you need a transformer ?
Wednesday, June 10, 2020
Relays vs. Solenoids vs. Contactors: A Comparison
Thursday, June 4, 2020
ABB Opens new distribution center in Phoenix!
Thursday, May 28, 2020
Search Posts |
|
|
Blog Categories
General
12/09/2020 - Voltage Monitor Relays
02/13/2019 - 5 Benefits of Industrial Ether
02/06/2019 - Remarkable Benefits of Liquid
01/30/2019 - Electrical Protection of Induc
01/16/2019 - 5 Causes of Motor Failure and
01/02/2019 - Everything You Need to Know Ab
12/28/2018 - Different Types of Soft Starte
12/12/2018 - Different Types of Programmabl
12/05/2018 - Variable Frequency Drive
11/30/2018 - Applications of Programmable L
11/14/2018 - The Importance of Relays
11/07/2018 - Everything You Need to Know Ab
07/27/2018 - What Are Unearthed Outlets & W
07/11/2018 - The Difference between a Light
07/02/2018 - How Can I Stop My Smoke Detect
06/29/2018 - Understanding Operator Interfa
06/13/2018 - The Importance of Brand Authen
06/04/2018 - Stepper Motors for Machine Aut
04/16/2018 - The Use of Soft Starters and I
04/02/2018 - The Types & Advantages of Usin
03/27/2018 - The New Designs of Contact Blo
03/27/2018 - Important Things You Need to K
03/14/2018 - Limit Switches Improve Safety
03/05/2018 - Soft Starters- Advantages, Typ
02/27/2018 - 8 Reasons to Use a Fuse
02/16/2018 - 4 Benefits of Programmable Log
02/06/2018 - 3 Reasons Why Circuit Breakers
01/29/2018 - 2 Gas Based Generators You Did
01/18/2018 - Common Types of Generators You
01/05/2018 - 3 Machine Safety Measures That
Enclosures
02/23/2019 - Different Types of Electrical
10/31/2018 - The importance of installing e
08/06/2018 - Metal or Plastic? How About Ne
Circuit Protection
09/12/2018 - Why Are Fuses Important?
08/31/2018 - Miniature Circuit Breakers: Ty
08/15/2018 - Miniature Circuit Breakers: Ty
05/30/2018 - How to Replace a Fuse
05/21/2018 - Circuit Breaker vs. Fuse: Whic
05/07/2018 - All You Need to Know About Cir
04/02/2018 - 5 Reasons Why Circuit Breakers
01/01/2018 - ABB Terminal Blocks Are Child’
01/25/2016 - Why Do You Want Miniature Circ
01/12/2016 - Lovato Now At Midwest Equipmen
Machine Safety
Midwest Enclosures
ABB New Facility
Relays vs. Solenoids vs. Contactors: A Comparison
Transformers
Gateway Convertors
New Mersen Product !
Supply Chain Shortages
Why is Motor Control Important ?
What Do Time Switches Do?
Understanding Time Delay Relay Functions
Using Liquid Level Control Relays
Intrinsically Safe Relays
|
Subscribe To Our Blog |
|